1. Field of the Invention
The present invention relates to a semiconductor manufacturing apparatus for manufacturing a thin film transistor device formed on a glass substrate of a large area and a manufacturing method for the thin film transistor. The present invention particularly relates to a laser crystallization semiconductor thin film formation apparatus using an ultraviolet pulse laser and a manufacturing method for a polycrystalline semiconductor thin film transistor.
2. Description of the Related Art
Heretofore, a transistor having a MOS (metal-oxide film-semiconductor) structure has been widely used for such as a large scale integrated circuit (LSI). Particularly, in silicon LSI manufacturing processes, since there is a thermal oxide step employing a high temperature process of about 1000xc2x0 C. for formation of a MOS structure on a silicon wafer, it is easy to produce a clean oxide film-silicon interface.
On the other hand, in manufacturing processes for formation of a so called high temperature polysilicon thin film transistor to be applied to liquid crystal light valves, after an a(amorphous)-Si thin film on a quartz substrate is crystallized by a solid phase growth, patterning and acid-cleaning are conducted for a silicon layer, and an oxide film formation at a high temperature of about 1000xc2x0 C. are conducted. Since a native oxide film formed at the time of the acid-cleaning is removed during heating, an oxide film is formed on a clean surface of the silicon layer.
However, in a low temperature polysilicon TFT process which is conducted at a temperature below 400xc2x0 C. using excimer laser annealing, since such a high temperature process can not be employed, means for removing the native oxide film on the silicon surface formed after the acid-cleaning is required. For this reason, a method to sequentially conduct formation of a silicon film, laser irradiation, patterning and cleaning of the silicon film, and formation of a gate insulating film are said to be general, and a cleaning step after patterning plays an important role in,stability and reproducibility of manufacturing processes.
For a way to solve such problems, M. Sekiya et al. has proposed the apparatus composed of an insulating film formation chamber, a laser irradiation chamber, and a hydrogenation chamber, all capable of transporting a substrate in vacuum, in IEEE ELECTRON DEVICE LETTERS, Vol. 15, No. 2, 1994 page 69. In this apparatus, after an amorphous silicon film formed on a glass substrate is crystallized by a laser, hydrogenation and formation of a gate insulating film are conducted sequentially in the same apparatus.
However, according to a manufacturing method using this apparatus, although the silicon surface after crystallization using the laser is kept clean, removal of a native oxide film produced before crystallization by the laser is insufficient. In other words, the native oxide film itself or impurity metal atoms contained in the native oxide film induces variations in the laser crystallization step whereby reproducibility of the process is deteriorated. Moreover, in a case where a subsequent step such as laser crystallization or formation of a thin film is performed after the silicon thin film previously formed is once exposed to the air, cleaning with cleaning liquid such as ammonia/hydrogen peroxide/pure water, hydrochloric acid/hydrogen peroxide/pure water, sulfuric acid/hydrogen peroxide, hydrofluoric acid/pure water or cleaning with heated liquid prepared by heating them must be conducted prior to a next step. The amount of these acid-alkaline type cleaning liquids to be used increases in accordance with an increase in a size of the glass substrate, resulting in an increase in a cleaning liquid cost and waste liquid cost.
On the other hand, the excimer laser annealing apparatus has required a wider setting area than before in accordance with an enlargement of a size of the glass substrate. Particularly, in the laser irradiation chamber, a size of the substrate is larger than an irradiation area, covered by one irradiation of the laser beam. As shown in FIG. 1, while horizontally moving the glass substrate 409 set in the vacuum container constituting the ELA (Excimer Laser Annealing) module 407, the entire surface of the substrate will be crystallized by laser irradiation. In case of such method, when the glass substrate 409 is moved only in one direction on the plane, the setting area of the vacuum container must be two times as large as a size of the glass substrate, and when the glass substrate 409 is moved in two directions on the plane, both directions being perpendicular to each other, the setting area of the vacuum container must be four times as large as the size of the glass substrate. Specifically, laser beam emitted from the excimer laser 401 travels along the optical path 402, and it passes through the A to C. optical apparatuses 404, 405, and 410 and the mirrors 403a to 403e, the optical apparatuses serving to shape the laser beam to the desired beam. After the laser beam is shaped to the desired beam, it reaches the surface of the glass substrate 409 through the window 406. The glass substrate 409 is fixed to the substrate holder 411 on the stage which is capable of moving in x- and y-directions on the plane. The glass substrate 409 undergoes laser irradiation on its desired region. In this case, the setting area of the vacuum container must be four times as large as a size of the glass substrate. More specifically, if a substrate has a length dimension, then the vacuum chamber has a dimension which is more than twice the substrate length. However, enlargement of the setting area is not desirable because of an increase in cost of clean room equipment. When a process room equipped with a plurality of functions is arranged in a limited setting area, the space of the laser irradiation room limits the space of a process room equipped with other functions.
Moreover, while keeping the semiconductor surface (interface) clean, although a wet cleaning step for the above-described substrate is omitted, when an irradiation step is conducted, there has been the following problem. Specifically, as disclosed in Japanese Patent Application Laid Open No. 5-211167, when laser irradiation is required for a certain region, (1) a system to previously form a marker for positioning and (2) a system to form an integrated circuit fitting to a region where the laser irradiation was conducted are needed.
In case of the system (1), after a certain thin film is formed, resist patterning using photolithography (PR) and thin film etching are conducted, and a marker is formed. Thereafter, cleaning is performed using the acid-alkaline cleaning liquid described above. Subsequently, a silicon thin film is formed, and laser irradiation fitting to the marker position is conducted, whereby a crystallized silicon thin film can be produced. Alternatively, as shown in FIGS. 2A to 2E, the silicon thin film 502 is first formed on the entire surface of the glass substrate 501 (FIG. 2A). The resist 506 is coated on the silicon thin film 502 (FIG. 2B). The resist 506 undergoes patterning using a photolithography technique, whereby the resist 507 for developing is formed (FIG. 2C). Thereafter, the mark portion 504 is formed by dry etching (FIGS. 2D and 2E).
On the other hand, in case of the system (2), a means for detecting the laser crystallization position using a certain method is required, and it is difficult to obtain a level positioning precision required by a stepper and the like. Also according to the system (1), an increase in cost due to an additional PR step and an additional cleaning step is incurred. In a case where a marker is formed directly on a silicon film, the surface of the silicon undergoes the PR step, so that cleaning with a precision is needed. A more simplified marker formation means is required.
The first object of the present invention is to provide a multifunction semiconductor manufacturing apparatus with a high stability, which is capable of eliminating cleaning steps using chemicals. The second object of the present invention is to provide a compact-sized semiconductor manufacturing apparatus which is capable of crystallizing a substrate by a laser without moving the substrate and promoting multi-function characteristics of the apparatus. Furthermore, the third object of the present invention is to provide mark formation means which requires needs no photolithography steps. Still further, the fourth object of the present invention is to provide a low cost and high performance thin film transistor manufacturing apparatus which is capable of keeping a silicon clean surface (interface).
A semiconductor manufacturing apparatus of the present invention comprises at least a silicon thin film formation chamber or a dry cleaning chamber, an insulator thin film formation chamber, a laser irradiation chamber, and a hydrogen annealing chamber, wherein a substrate on which a semiconductor device is formed can be transported between treating chambers without being exposed to the air.
For a laser irradiation means in the semiconductor manufacturing apparatus of the present invention, a laser light source and an optical system for shaping a laser beam from the laser light source are provided, which is constituted such that said laser beam is irradiated onto a substrate set in a vacuum container. Part of the optical system is disposed within said vacuum container, and the part of the optical system disposed within the vacuum container moves relative to the substrate whereby the laser beam can be irradiated onto the entire surface of the substrate or almost all regions thereof. In this case, an area irradiated by one laser beam is smaller than the area of the substrate, and the laser beam is irradiated onto the substrate without changing the optical path of the optical system. Alternatively, for a laser irradiation chamber, first and second laser light sources are provided, wherein a laser beam from said first laser light source and a laser beam from said second laser light source are individually or simultaneously irradiated onto the substrate set within the vacuum container.
Furthermore, the thin film transistor manufacturing method of the present invention comprises the steps of: forming a silicon thin film on a glass substrate; irradiating a laser onto said silicon thin film thereby obtaining a re-crystallization silicon film; performing a hydrogen plasma treatment for said re-crystallization silicon film thereby terminating dangling-bonds of the silicon; and forming a silicon dioxide film on said re-crystallization silicon film, wherein said steps are performed under conditions of not being exposed to the air and at a processing temperature of 350xc2x0 C. or less. Alternatively, the thin film transistor manufacturing method of the present invention comprises the steps of: forming a silicon thin film on a glass substrate; forming a silicon dioxide film on said silicon thin film; irradiating a laser onto said silicon thin film thereby obtaining a re-crystallization silicon film; and performing a hydrogen plasma treatment for said re-crystallization silicon film thereby terminating dangling-bonds of the silicon, wherein said steps are performed under conditions of not being exposed to the air arid at a treatment temperature of 350xc2x0 C. or less. These manufacturing methods should include a removing step for the silicon thin film using a laser after formation of the silicon thin film.